1. Field of the Invention
The present invention relates to an optical transmission component and a production method thereof, particularly to an optical transmission component and a method for producing the optical transmission component by assembling an optical transmission line such as an optical fiber and a holder having an optical function.
2. Description of the Related Art
FIG. 1 shows a schematic perspective view of a conventional optical transmission component (refer to, for example, Japanese Patent Application Laid-Open No. 2003-107277). An optical transmission component 11 includes an optical connector 12 and a lens array 13. In the optical connector 12, cores 17 of an optical fiber array 16 (tape core) are sandwiched between an upper-side holder 14 and a lower-side holder 15, and end faces of the cores 17 are exposed to a front face thereof. In the lens array 13, a plurality of lenses 18 are formed in a front face thereof, a pitch between the lenses 18 is equal to a pitch between the cores 17. A backside of the lens array 13 is bonded to a front face of the optical fiber array 16 with a bonding agent such that optical axes of the lenses 18 are aligned with center axes of the cores 17.
In the optical transmission component 11 having the above-described configuration, during a production process, it is necessary that the backside of the lens array 13 be bonded to the front face of the optical connector 12 with the bonding agent while the optical axes of the lenses 18 are aligned with the center axes of the cores 17, which results in cost increase and time-consuming assembling work or alignment.
Therefore, the inventors have an idea that the lens array is integrally molded with the holder portion of the optical connector from the beginning. When the lens array is integral with the holder portion, it is not necessary to bond the lens array to the optical connector, so that the optical axes of the lenses can automatically be aligned with the center axes of the cores by positioning the cores in the holder portion of the optical connector.
However, when the lens array is integral with the holder portion, there is generated a new problem. When a space is formed between the backside of the lens array and the end face of the core, the light is reflected by the end face of the core or the backside of the lens array, or the light leaks from the space, which results in a decrease in optical coupling efficiency. Although the space between the backside of the lens array and the end face of the optical connector is filled with the bonding agent, peel-off of the bonding agent or a bubble (micro peel-off) is generated in the backside of the lens array due to curing shrinkage after filling of the bonding agent and a difference in thermal expansion coefficient among the lens array, the holder, the bonding agent after curing, and a fiber material. The light is scattered due to the peel-off and the bubble, and the optical coupling efficiency is largely decreased between the optical fibers. The investigation shows that a difference in linear expansion coefficient between a resin portion (connection member) connecting the lens array and the optical connector and the bonding agent with which the space between the lens array and the optical connector is filled has a large influence on the generation of the peel-off and bubble rather than the curing shrinkage of the bonding agent.
In view of the foregoing, an object of the present invention is to provide an optical transmission component and a production method thereof, wherein the peel-off and the bubble are not generated within a keeping temperature range in the bonding agent with which the space between the optical function portion and the end face of the optical transmission line is filled while the holder portion for holding the optical transmission line such as the optical fiber and the optical function portion such as the lens array are integrally molded.